AR4 on “1998 was the warmest year”

As most CA readers know, a few years ago, I wondered how they knew that 1998 was the warmest year in a millennium – a claim that you don’t see in AR4. Nor, at first (second or even fifth) glance does the assertion, once so prominent, even seem to be addressed in AR4.

The Climategate letters offer an interesting vignette. Chapter 6 authors were not unaware of the matter and worked over language on the issue like New York or London lawyers, eventually inserting a clause deep in the chapter that gave them cover, intentionally leaving the issue out of the chapter Executive Summary.

On July 28, 2006, Chapter 6 Coordinating Lead Author Overpeck (1154090231.txt) wrote to Briffa (copy Jansen) passing along a question from WG1 Chairman Susan Solomon, asking the reasonable question about what happened to claimes that 1998 was the warmest year, 1990s the warmest decade.

Hi Keith – in our TS/SPM discussions, Susan has raised this question:
“In the TAR they spoke of 1998 being the warmest year in the
millennium and the 1990s the warmest decade. I don’t see that
chapter 6 addresses any of these time scales. I am not saying you
should do so – but are you planning to say anything about it and why
you aren’t doing so? and if you’re not planning to say anything at
all, can you please tell me what you think about it, just for my own
info?”

Would you please give me your feedback on this, with enough
thoughtful detail to hopefully make me/Susan fully informed (a para
should be enough).
Thanks, Peck

On Aug 1, 2006, Briffa replied (728. 1154484340.txt) with a comment that would not be out of place at Climate Audit (one of the interesting things about Climategate letters is how often they express views in private that are expressed publicly at CA). Briffa:

Peck,
The TAR was, in my opinion, wrong to say anything about the precedence (or lack thereof) of the warmth of the individual year 1998. The reason is that all reconstructions have very wide uncertainty ranges bracketing individual-year estimates of part temperature.

Given this, it is hard to dismiss the possibility that individual years in the past did exceed the measured 1998 value. These errors on the individual years are so wide as to make any comparison with the 1998 measured value very problematic, especially when you consider that most reconstructions do not include it in their calibration range (curtailed predictor network in recent times) and the usual estimates of uncertainty calculated from calibration (or verification) residual variances would not provide a good estimate of the likely error associated with it even if data did exist.

Now Briffa didn’t leave it quite like that. He continued with the opinion that confidence could be attached to decadal averages that could not be attached to individual years:

I suspect that many/most reconstructions of NH annual mean temperature have greater fidelity at decadal to multidecadal timescales (based on examination of the covariance spectrum of the actual and estimated data over the calibration period. This is the reason many studies implicitly (Hegerl et al.,) or explicitly (Esper et a;., Cook et al.) choose to calibrate directly against decadally-smoothed data.

The exception is the Briffa et al (tree-ring density network based) reconstruction back to 1400. This has probably the best year-to-year fidelity – but for summer land only and does not go back anyway to the MWP.

We are on much safer grounds focusing on decadal/multi-decadal timescales and so this is where we place the emphasis. As for the warmest decade’ – this is likely to be the 1990s or the last 10 years – but again, the proxies do not cover this period, and we do anyway state that post 1980 is the warmest period – which I think is fair enough.

Overpeck (728. 1154484340.txt) acknowledged this message the next day, passing it on to Solomon and Jansen:

Hi Keith – thanks. This makes sense to me. I’ll cc Susan so she understands the issue better, and also can advise on any strategy we should adopt to make sure we communicate effectively.
thanks again
best, peck

On Sep 1, 2006 (739. 1157138720.txt), Overpeck and Jansen adopted the strategy of inserting some protective language in the chapter text, while leaving it out of the Executive Summary, and urgently requested Briffa to write some language on the matter (it had not been specifically addressed in the drafts sent to reviewers).

As for the 1998/2005 warmest in last 1000 years issue, we suggest adding nothing new to the ES, in line with our chapter policy from Bergen, BUT adding something in the chapter along the lines of: ” There is currently insufficient knowledge to form a consensus on the issue of how the warmth of individual years of the last 100 years compare with individual years of the last 1000 years” Keith, would you like to make a suggestion on the wording and placement?

On Sep 13 (744. 1158180188.txt), Briffa reverted with some language that was carefully crafted to say the least.

Eystein and Peck
I have thought about this and spent some time discussing it with Tim. I have come up with the following

Greater uncertainty associated with proxy-based temperature estimates for individual years means that it is more difficult to gauge the significance, or precedence, of the extreme warm years observed in the recent instrumental record. However, there is no new evidence to challenge the statement made in the TAR that 1998 (or the subsequent near-equivalent 2005) was likely the warmest in the last 1000 years.

This should best go after the paragraph that concludes section 6.6.1.1. I believe we might best omit the second sentence of the suggested new paragraph – but you might consider this too subtle (or negative) then. I think the second sentence is very subtle also though – because it does not exclude the possibility that the same old evidence that challenges the veracity of the TAR statement exists now , as then!

I think this could go in the text where suggested , but I think it best NOT to have a bullet about this point. We need to check exactly what was said in the TAR . Perhaps a reference to the Academy Report could also be inserted here?

Anyway, you asked for a straw-man statement for all to argue about so I suggest we send this to Stefan, David , Betty and whoever else you think.
cheers
Keith

Overpeck wrote back the same day ( 744. 1158180188.txt):

Keith – thanks for this and the earlier updates. Stefan is not around this week, but hopefully the others on this email can weight in. My thoughts…

1) We MUST say something about individual years (and by extension the 1998 TAR statement) – do we support it, or not, and why.
2) a paragraph would be nice, but I doubt we can do that, so..
3) I suggest putting the first sentence that Keith provides below as the last sentence, in the last (summary) para of 6.6.1.1. To make a stand alone para seems like a bad way to end the very meaty section.
4) I think the second sentence could be more controversial – I don’t think our team feels it is valid to say, as they did in TAR, that “It is also likely that, in the Northern Hemisphere,… 1998 was the warmest year” in the last 1000 years. But, it you think about it for a while, Keith has come up with a clever 2nd sentence (when you insert “Northern Hemisphere” language as I suggest below). At first, my reaction was leave it out, but it grows on you, especially if you acknowledge that many readers will want more explicit prose on the 1998 (2005) issue.

Greater uncertainty associated with proxy-based temperature estimates for individual years means that it is more difficult to gauge the significance, or precedence, of the extreme warm years observed in the recent instrumental record. However, there is no new evidence to challenge the statement made in the TAR that 1998 (or the subsequent near-equivalent 2005) was likely the warmest of Northern Hemisphere year over the last 1000 years.

5) I strongly agree we can’t add anything to the Exec Summary.
6) so, if no one disagrees or edits, I suggest we insert the above 2 sentences to end the last (summary) para of 6.6.1.1. Or should we make it a separate, last para – see point #3 above why I don’t favor that idea as much. But, it’s not a clear cut issue.

Thoughts? Thanks all, Peck

David Rind weighed in (744. 1158180188.txt) as follows (copies to other Lead Authors)::

Leaving aside for the moment the resolution issue, the statement should at least be consistent with our figures. Fig. 6-10 looks like there were years around 1000 AD that could have been just as warm – if one wants to make this statement, one needs to expand the vertical scale in Fig. 6-10 to show that the current warm period is ‘warmer’. Now getting back to the resolution issue: given what we know about the ability to reconstruct global or NH temperatures in the past – could we really in good conscience say we have the precision from tree rings and the very sparse other data to make any definitive
statement of this nature (let alone accuracy)? While I appreciate the cleverness of the second sentence, the problem is everybody will recognize that we are ‘being clever’ – at what point does one come out looking aggressively defensive?

I agree that leaving the first sentence as the only sentence suggests that one is somehow doubting the significance of the recent warm years, which is probably not something we want to do. What I would suggest is to forget about making ‘one year’ assessments; what Fig. 6-10 shows is that the recent warm period is highly anomalous with respect to the record of the last 1000 years. That would be what I think we can safely conclude the last 1000 years really tells us.
David

Jansen (745. 1158204073.txt) suggested a version without Briffa’s casuistic second sentence:

Hi all,
My take on this is similar to what Peck wrote. My suggestion is to write:

Greater uncertainty associated with proxy-based temperature estimates for individual years means that it is more difficult to gauge the significance, or precedence, of the extreme warm individual years observed in the recent instrumental record, such as 1998 and 2005, in the context of the last millennium.

think this is scientifically correct, and in essence means that we, as did the NAS panel say, feel the TAR statement was not what we would have said. I sympatise with those who say that it is not likely that any individual years were warmer, as Stefan has stated, but I don´t think we have enough data to qualify this on the hemispheric mean.
Best wishes,
Eystein

On Sep 15, 2006, Fortunat Joos wrote that if there isn’t enough evidence to say whether 1998 was the warmest year or not, they should say so.

Hi,

I support Eystein’s suggestion and agree with David.

If there is not sufficient evidence to support or dismis claims whether 1998 or 2005 was the warmest year of the millennium than we should indeed say so. It is the nature and the strenght of the IPCC process that points from the TAR and earlier reports get reconsidered and reassessed. It is normal that earlier statements get revised. Often statements can be strenghtened, but sometimes statements can not be supported anymore. Our job is to present the current understanding of science as balanced as possible.

With best wishes,
Fortunat

A little later, Briffa signed off on the revision, noting his own reservations about the original “too clever” language, expressing a slight worry that they had “inserted this late with no refereeing and no justification in the text” – (a scruple that he and Jones didn’t worry about when it came to matters MM):

I do not disagree either – in fact I preferred not to make the “too clever” second statement in my “straw man” as I said at the time. If this is the consensus (and I believe it is the scientifically correct one) then I would be happy with Eystein’s sentence. The worry is that we have inserted this late with no refereeing and no justification in the text. I would also suggest dropping the second “!individual” in the sentence.

On Sep 15 (746. 1158324958.txt), Overpeck decided to go with Jansen’t language on the “all important 1998 sentence”.

Thanks Keith, Tim and Fortunat for your input. We’ll go with what we have then – Eystein’s suggestion minus the second “individual”. Eystein and Oyvind – just want to double check that you’ve deleted that 2nd “individual” in the all important 1998 sentence??
Thanks, Peck

In the AR4 Final Version, section 6.1.1.1 ended as follows;

Greater uncertainty associated with proxy-based temperature estimates for individual years means that it is more difficult to gauge the significance, or precedence, of the extreme warm years observed in the recent instrumental record, such as 1998 and 2005, in the context of the last millennium.

AR4 agreed with MM on the “warmest year in 100 years”. Who would have known?

Which leads to another question. What caused the WG1 authors to have a more guarded opinion in AR4 about “1998 is the warmest year” than in AR3? What was their justification for modifying the opinion of AR3 (relying on the statistical analysis of MB98-99) that they knew with statistical confidence that 1998 was the “warmest year”?

In the penultimate comment above, Briffa observed that there was “no justification in the text” for introducing this more guarded opinion in the conclusion to the section.

The obvious location in the text for justifying this more guarded opinion was in the discussion of the MM papers, which had, after all, raised this issue. After the MM papers observed the abject failure of MBH verification r2 statistics in the early segments, even MBH supporters abandoned any pretence that the reconstruction had any “inter-annual skill”. This point is conceded in a couple of Climategate letters though not publicly.

But Briffa, as the author of the relevant section, did not concede even this point in the text on MBH vs MM – a point would have provided a small bit of credit to MM. Worse, between the Second Draft (submitted to reviewers) and the Final Draft, during surreptitious correspondence with Briffa, Eugene Wahl, neither an IPCC author or reviewer, inserted a statement that our analysis had a negligible impact – a statement that was contrary to the corresponding Second Draft statement and a statement that was never submitted to reviewers.

Ironically, Chapter 6 Lead Authors adopted a key position of the MM papers in respect to individual years (though not yet individual decades) – a position that clearly contradicted MBH98-99 and AR4 – but failed, as Briffa observed, to document the changed view in the running text.

East Anglia folks seem consistent in their meaning for “clever.” Something is clever if it is knowingly misleading.
Reflects well on Jansen and Joos that they steered Peck and Briffa away from cleverness.

That’s correct… the standard British / Irish meaning of the term is devious / deceptive, not intelligent. A “clever” solution should be viewed with skepticism and mistrust in the UK and the RoI, not with admiration.

What’s extraordinary about these email exchanges is that they expose such a high level of uncertainty about the nature of the underlying trends and norms. These people need to parse their words so legalistically because they simply don’t know what’s true in the science. They’re simply making assertions up out of whole cloth. It’s breathtaking (and revolting) to witness.

In my opinion, they recognize that there have been major mistakes and misrepresentations in climate science. John A stated above that the emails rather clearly show that they are aware of this. Most of the team is so deeply embedded in the process of deception that they would put their own careers at risk if they were more clear in their statements.

I actually like how this post provided insight to how this statement came about. I actually think that the authors in this case did a good job of not being pushed towards making rash overstatements like TAR. I don’t think that making the insulting commentary (like peter Dunford did, letting our bias get in the way are we?) is warranted under this circumstance. People can do things right in some instances even though in other aspects they make grievous errors.

I would surmise that you are not an engineer. In the engineering world it does not matter whether you think you are right or whether your calculations are right. Both of these may be the case and the bridge will still fall down or the dam will still fail. It is an unforgiving discipline and the feedback is often quite immediate and cannot be argued with or away. I took Mr. Dunford’s comment not as bias but as one who, like myself, has been involved in a discipline that requires a completely different mindset when it comes to uncertainties and conclusions.

In fact, even when our science is correct and the calculations are correct, good engineering practice requires over-engineering or the use of safety factors as failure (of a structure) often leads to loss of life. Thus, even when our best science and our best calculations lead us to a particular conclusion, we still build in a safety factor or “fudge” factor into our conclusions so that they are scaled back significantly just in case. The result of this mindset is that engineering is very successful in avoiding failures, although even the most conservative of approaches cannot eliminate them.

In contrast, many in Climate Science take a much riskier approach when evaluating their uncertainties and reaching their conclusions. In short, what you may see as a “bias” may not be arbitrary but, instead, I would submit may be based on many years of treating uncertainties and reaching conclusions in a much more conservative manner and with a great deal more rigor.

I’ve been pondering why so many engineers have doubts about catastrophic global warming and agree with Phil it is the discipline of risk. To the general public a 95% certainty seems high, to an engineer the certainty 99.999% is the point at which certainty starts to have some meaning. “Very likely” as spattered throughout AR4 will frighten the public and the politicians, but to engineers, without further testing and proof it will have no meaning whatsoever.

I’m an engineer and for areas like this, if I could be shown something with 80 pct certainty, I’d probably buy in. A claim of 95% certainty is just not credible and therefore automatically rejected. Especially now.

Engineers will typically have a major problem with anyone claiming something with no data to back up their claims. As an engineer, I want to see the data. I may not be able to review it myself, but I have engineers on my team who can review it. When anyone claims something and then refuses to show their data and methods, I infer that they are hiding something. The burden of proof is on the claimant, not on me or my team.

When I see data graphed without error bars, I am going to be skeptical of the graph. When I see that the propagation of errors is not understood by the author of a paper, I do not accept the paper’s conclusions without reviewing the data and the errors myself.

Which leads to another question. What caused the WG1 authors to have a more guarded opinion in AR4 about “1998 is the warmest year” than in AR3? What was their justification for modifying the opinion of AR3 (relying on the statistical analysis of MB98-99) that they knew with statistical confidence that 1998 was the “warmest year”?

In the penultimate comment above, Briffa observed that there was “no justification in the text” for introducing this more guarded opinion in the conclusion to the section.

The obvious location in the text for justifying this more guarded opinion was in the discussion of the MM papers, which had, after all, raised this issue. After the MM papers observed the abject failure of MBH verification r2 statistics in the early segments, even MBH supporters abandoned any pretence that the reconstruction had any “inter-annual skill”. This point is conceded in a couple of Climategate letters though not publicly.

But Briffa, as the author of the relevant section, did not concede even this point in the text on MBH vs MM – a point would have provided a small bit of credit to MM. Worse, between the Second Draft (submitted to reviewers) and the Final Draft, during surreptitious correspondence with Briffa, Eugene Wahl, neither an IPCC author or reviewer, inserted a statement that our analysis had a negligible impact – a statement that was contrary to the corresponding Second Draft statement and a statement that was never submitted to reviewers.

Ironically, Chapter 6 Lead Authors adopted a key position of the MM papers in respect to individual years (though not yet individual decades) – a position that clearly contradicted MBH98-99 and AR4 – but failed, as Briffa observed, to document the changed view in the running text.

In the exchange of emails, wasn’t it established that the claim that 1998 (or 2005) was the warmest of the past 1000 years (or that the 1990’s decade was the warmest) could not be supported because the means of determining prior temperatures did not produce agreement with the current instrumental record? Wasn’t the divergence (at least in a round-about way) acknowledged to have thrown the claim of warmest year or decade (based on Mann, Jones and Briffa reconstructions) out the window?

The hot 1998 subject should not have even have been mentioned unless a researched scientific explanation of its cause was given. After 3 years of looking, I still can see no reason for the 1998 anomaly.

So they resorted to English expression.

There is a current example doing the rounds, which says approximately “The Earth continues to get hotter because the decade ending 2009 has the highest average of all decades measured since 1850”. OTOH, the temperature from 1999 to 2009 does not appear to be rising, which can lead to the opposite conclusion. As has been noted often before, the choice of starting date can influence the outcome. And the “weather” versus “climate” discussion is involved, though there is no supportable reason for the distinction.

The lesson is to avoid the mistake of purposely distorted meaning in the material we all write.

Well, it is clear that one should not view sausage being made. It just does not sit right with me that claims keep being insisted on about individual years and decades with respect to 1000 years when the confidence intervals on the recons are a mile wide (especially when the manner of creating the confidence intervals is probably conservative).

As I understand it, the NAS report and W&A’s paper explain the meaning of RE and CE statistics: RE shows that long-term trends are meaningful and CE shows that year-to-year trends are meaningful. Perhaps I’m being overly extreme, but statements in an abstract about a single year (1998 or 2005) were either MISTAKEN (requiring retraction) or FRAUDULENT when the author knew that the CE is zero.

I don’t understand Briffa’s argument that “examination of the covariance spectrum” allows greater confidence to be placed on decadal averages, but such an examination would need to be published in a peer-reviewed paper to be suitable for use in the 4AR.

The IPCC needs a policy for disclosing the changing statistical foundation for statements made in earlier Summaries for Policymakers. What should be done when Paper A finds a statistically robust effect and Paper B does not? The answer depends on whether fundamentally the same data set is being analyzed or new data has been developed; as well as what the authors think about the quality of the new vs old data. It also depends on the statistical certainty in Paper B – Is it very likely, likely, or more likely than not that Paper A reached the wrong conclusion?

The need for a policy on updating should be obvious. From a statistical point of view, 1 out of 20 conclusions drawn from a single experiment with 95% certainty are wrong (and many others contain systematic errors), so every SPM must contain mistakes. Conclusions made with lower degrees of significance are worse (and usually don’t belong in a scientific document). Knowing that future corrections might need to be made could limit the amount of alarmist rubbish that gets included in SPM’s.

The TAR was, in my opinion, wrong to say anything about the precedence (or lack thereof) of the warmth of the individual year 1998. The reason is that all reconstructions have very wide uncertainty ranges bracketing individual-year estimates of part temperature.

Right – the earlier in the dialog, the more honest is the dialog. The more they massage it, the less honest it is – BY INTENT AND AGENDA. As the “hide the decline” emails showed, it was all about remaining on message and not letting ANY deflections from message get through. While the IPCC summaries are political documents, arguments that the politicians were the only ones twisting the facts (which is why quite a few scientists resigned from the IPCC over the years) are not telling the entire story. The emails showed the scientists were not only on board with the program, but active distorters of the truth – for their OWN purposes. The pols and scientists were collectively two peas in a pod.

…But also the importance of the “uncertainty ranges”/bars means those single-line traces in all the graphs are VERY inexact. Anyone who points at the LINE and says it means +0.35C or +0.21C have no idea of the uncertainty of every graph, especially those which include proxies. (And that argument doesn’t even include the fudging that was going on with the numbers.) And the further back they go, the more the uncertainty. Many of those decades only have a few proxies at isolated places on the globe. Yet they supposedly represent the entire world.

But then when someone today points to the US – with the most dense geographical and temporal instrument record on the planet – as not having warmed during a certain period, or as Steve got them to admit 1934 being warmer than 1998, and what is the first thing out of their mouths? “Oh, that is only the US! It doesn’t represent the entire world. What is the matter with you people, anyway? Don’t you know the difference between weather and climate?”

But they take proxies – which are influenced strongly by rainfall as well as temperature – in a few locations and tell us that FOR THE ENTIRE GLOBE the 15th century or the 6th century BCE or the 7th millennium BCE that those proxies, with all their uncertainties, can tell us what the climate was for decades and centuries. For the entire globe.

The 21st and 22nd had thunderstorms so that meant 108 F with like 80% humidity. I have re-checked 1998 and it was a soothing mist compared to ’88. The winter before was bitterly cold with orange groves dying of
frost in the central valley, a year of great extremes. Likely the yearly average may not be that high due to the combination and that some other year may be higher due to a very mild winter and merely hot summer.

In Fig 8 :most of the charts show equal or inferior t° / max. past t°, only NW region current situation is above past t° … and the final result is …… global Europe is above any past t°.
Authors say MWP is a local phenomenom but neither in the NE or NW chart we see it.

I heard a strange comment from an IPCC lead author this week at the European Geosciences Meeting (EGU).

On Tuesday the EGU held a promising “Great Debate” on the question: “To what extent do humans impact the Earth’s climate?” Mike Lockwood, Bernard Legras and Günter Blöschl gave thoughtful technical presentations about what we know and don’t know about the technical issues related to solar variability, climate trends and hydrology, among other things.

However, the other speaker, Franz Berkhout, an IPCC lead author, eloquently glossed over the technical issues to argue passionately for action. When asked by an audience member if the mixing of politics into climate science might adversely affect the science, he responded: “Thank God!” Apparently Berkhout believes that scientists’ “social contract” requires, above all else, service to the public — whatever that means.

I was not sure if Berkhout misunderstood the question, or perhaps he really believes that science should be adversely affected by politics. In some sense, it does not matter.

Given representatives like this, I do not see how IPCC is ever going to re-establish its credibility.

But this is not the purpose of this blog. One question remains with the Climategate: Was it a “trick” to hide “An Inconvenient True ….Result” or a “trick” as any good marketing business teams provides to find the best way to present a result ? …the answer in this blog….

A belgium author once said “A lie that doesnot have the decency to make us dream, is a crime against hope and against the essence of life”
(sorry for the very poor translation from french)

Wow, still digging for nuggets to distort in other peoples emails to make your case?

The assault on climate science didn’t start recently, so if I were writing AR4, and already had experience with non-scientists making bogus science arguments, hostile financial interests, and others who would make much of a peak year followed by a series of less peak but still darn warm years, I’d consider not listing that as a highlight too, it would only lend fodder to those who advance bogus arguments.

But as has been noted above, a record warm year is not about climate, while record warm decade* is, so leaving it out isn’t remarkable, it’s inclusion as anything other than an anecdote would be.

*Like the current decade in the instrumented record, that immediately follows the previous warmest decade in the instrumented record.

Impossible to answer since 1998 was such an anomaly. In fact, this year or next could be a similar warm anomaly which would stand for the next 10 years. There’s a lot of variability in the climate system.

But if 2009, 2010, or 2011 turns out to warmer, what will be your next argument for why the warming is insignificant?